Basics

This Page Aims to Lay Out The Existing Methods of Post-Processing 3D Printed Things
It also will organize methods that need further investigation

Existing Methods

Pretty straightforward
Needle Files , Deburring Tools , and Sandpaper rest is self explanatory
- Also maybe a Microfiber Cloth / "bath" in the sink or a Parts Washing Bin to clean off any Microplastics / burnt bits
A Hot Air Gun / SMD Electronics Rework Station can be used for small details like Stringing related "fuzz" ~~or just a Butane Lighter if you are desperate~~
Main Downside is Time Spent

A Rotary Tumbler or Vibratory Tumbler can be used for some parts
Given how much of a "rough process" this is, it cannot be used for more delicate prints
It is a High Volume Batch Process though, so that can have it's advantages in time savings

Also known as "Sandblasting"
Media Blasting is the more broad concept, and especially given the hardness of (most) FDM 3D Printed Plastics, a less "aggressive" media is most likely required
Would need to look into the existing literature on all this
In theory could something like Plastic Pellets / Plastic Regrind be used?

This only works for certain plastics, but a Solvent (Typically Water or Acetone ) is vaporized in a chamber, the print is placed in there, and the vapor (partially) dissolves the surface of the material
After a certain time period of exposure, the part (or the solvent if done in some fancy Solvent Recovery method, Vacuum + Bakeout ?) is removed
- The solvent then evaporates leaving behind a smoothed (but sometimes deformed, reducing/predicting and accounting for this is key) surface
(akin to Recrystalization / Zone Melting removing impurities, it does the same but for surface finish impurities)
Main Downside is Solvent Cost (especially if Solvent Recovery (short of "don't dump the bucket down the drain until all of it was used/evaporated") isn't done) and the potential for part deformation)

Given they are Thermoplastics , FDM 3D Prints Can Be Either Re-melted, or Simply Heated Up
This allows layer lines to "blur" and the part fuse into a single stronger one, or it can simply work in a manner similar to Post-Weld Heat Treatment
In order to prevent part deformation/drooping etc this is typically done in some sort of media
CNC Kitchen et al have documented using Plaster and Table Salt (Check if Iodonized Salt or just straight up Sodium Chloride (Although Did it also contain Anticaking Agents ...) )
It needs to be studied, but if something along the lines of Chopped Glass Fiber / Chopped Carbon Fiber were used (or to an extent maybe just Carbon Black ), could something akin to Case Hardening be achieved?

This does not fix the core issues of Layer Lines etc, but can achieve the desired Surface Finish / aesthetics
Certain processes, especially as shown by SLS 3D Printing may benefit from the more rough and/or porous surface finish (Perhaps a Synergy Between Dissolvable Annealing Media and this then)

ASMBL (A Process that Solves The Problem of 3D Print Post-Processing in a Manner Similar To How Machine Finishing of Castings Addresses Metal Casting Defects . It is done "by layer" (or potentially every 5 layers etc to minimize the amount of toolchanges and thus save time) however to be able to still produce the Novel Designs allowed by 3D Printing
Chemical Dipping vs Vapor Smoothing
- That BigRep Article Mentions the Former, but i haven't heard of it until then, and i wonder how the reaction rate is different (is the "melting" far more drastic?)